The invention relates to a sheet metal work center.
Generally in sheet metal working technology, for example in sheet punching, certain components are always needed. These include punches, a releasing plate or a releaser, and a lower tool or a so-called cushion. In sheet punching, the machining is conducted in a way that a punch is used to make a hole in a sheet against the lower tool or cushion, and the punch is drawn out of the hole either by a spring force or by another force, wherein the releasing plate prevents the punched sheet to rise with the punch, the plate remaining in its place. In sheet punching, there are two possibilities to conduct the machining: first, the releasing plate is in contact with the sheet to be punched during each punching stroke; or second, there is a certain air gap between the material to be punched and the releasing plate. Each method has its own advantages, i.e., when there is a contact with the plate at the punching stage, the plate will not vibrate during machining.
In current sheet metal working centers, stopping structures are still in use which have a mechanical connection with the machine bed. Height adjustments of the stopper in relation to the working level of the sheet to be machined are Known e.g. from the publication U.S. Pat. No. 5,136,521. However, the adjustment arrangements are made in a way that the full mechanical connection of the stopper to the machine bed is maintained. This results in several problems.
It is an aim of the present invention to eliminate the disadvantages involved in current constructions of sheet metal work centers, particularly in connection with stopper structures, and simultaneously to present new, surprising functional improvements in the functions of the stopper structures of sheet metal work centers. For achieving these aims, the sheet metal work center according to the invention has a lower tool that is adaptable to be driven to a number of positions for achieving different functions.
In particular, the basic idea in the present invention is to fix the lower tool of the stopper with a vertically movable transfer device, particularly a cylinder-piston mechanism using a pressurized medium. This solution gives, first of all, the advantage that the possibility of moving the transfer device can be utilized in automatic exchange of the lower tool. Using the transfer device, the functional parts of the stopper structure can e.g. be transferred underneath the working level into a position in which the lower tool can be released from the connection with the transfer device, e.g. with a manipulator. Secondly, the arrangement makes it possible to compensate for the effect of grinding operations that need to be made on the lower tool at regular intervals during its service life, on the thickness of the lower tool and thus on its position in relation to the working level. Thirdly, the transfer device makes it possible to implement forming by using the stopper structure in the sheet metal work center, i.e. the sheet can be machined from underneath the working level. Further, a fourth advantage of providing the transfer device with a cylinder-piston mechanism using pressurized medium is that the noise and vibration level of the sheet metal work center can be reduced to a considerable extent, because the impacts of the buffer do not hit the stationary body directly but the pressurized medium inside the cylinder-piston mechanism. This gives the necessary slight springiness which softens the working operation, and simultaneously the noise and vibration.